Cake frostings made primarily of powdered sucrose and milk or, alternatively, powdered sucrose, water, and butter, are well known to bakers and consumers of cakes the world round. Other fats, such as margarine and shortening, are often substituted for the butter and various other ingredients, including eggs, flavorings, colorings, and emulsifiers, are commonly used. These frostings are prepared by vigorously mixing together the ingredients. After preparation, the homogeneous and aerated frosting is immediately spread upon the exposed surface of the cake. In addition to providing enhanced taste and eye appeal to the cake, the frosting helps reduce the tendency of the cake to dry out.
The organoleptic properties of these frostings are well known. Initially, their texture is smooth; their consistency is short (as opposed to stringy); their viscosity is such that the frostings are easily spreadable, but do not flow or "run" on the cake; and their density is only about one gram per cubic centimeter due to their high level of aeration. The organoleptic properties of these frostings change over time when exposed to ambient air. The frostings dry (i.e., lose water), harden, and (as the sucrose crystallizes) become grainier in texture. The frostings also lose their aeration so that their density increases and their initially-smooth appearance becomes jagged. The change in properties over time of these frostings is so well known and accepted that it is not often considered a disadvantage. However, if given a choice, a frosting which maintained its original organoleptic properties would be preferred.
There is nothing particularly difficult about preparing a frosting, but it does take effort in obtaining the ingredients, mixing them, and then cleaning up the utensils. Accordingly, there is a demand for "ready-to-spread" frostings which can be stored at room temperature for long periods of time and then be applied directly from a container to a cake without mixing.
Conventional cake frostings are not suitable for use as ready-to-spread frostings because they are prone to rapid microbial spoilage due to the presence of dairy ingredients and because of their tendency to deaerate and otherwise lose their initial physical properties. Commercial storage-stable ready-to-spread frostings first appeared about 25 years ago. To minimize microbial spoilage and thereby extend shelf life, these frostings generally eliminated dairy ingredients and added various preservatives (e.g., citric acid, sorbic acid, potassium sorbate, and sodium benzoate). Even without dairy ingredients, preservatives were needed because these frostings had relatively high water activities which provided a good environment for the growth of microorganisms such as bacteria, yeasts, and molds. Water activity is the ratio of the vapor pressure of water in a material to the vapor pressure of pure water at the same temperature. It is well known that microorganisms have limits on their ability to prevent the loss of water from their cells. If the water activity of their environment is too low, the cells cannot regulate the water loss and either become dormant or die. For example, few bacteria can survive at water activities less than about 0.85, few yeasts can survive at activities less than about 0.80, and few molds can survive at activities less than about 0.71. Many different ready-to-spread cake frostings have been formulated in an attempt to create a frosting which would match the organoleptic properties of conventional frostings and which would maintain these properties upon storage.
Bedenk, U.S. Pat. No. 3,194,666, issued July 13, 1965, and Bedenk U.S. Pat. No. 3,253,928, issued May 31, 1966, disclose storage-stable ready-to-spread frostings which comprise about 45 to 75 weight percent sucrose, about 10 to 25 weight percent water, and about 5 to 30 weight percent of a particular shortening blend of partially hydrogenated glycoside base stock and substantially completely hydrogenated triglyceride hardstock.
Wahba, U.S. Pat. No. 3,464,830, issued Sept. 2, 1969, discloses a storage-stable ready-to-spread frosting having a small amount of an alkali metal pyrophosphate to improve color retention. Wahba discusses various techniques which have been used to produce storage-stable ready-to-spread frostings, e.g., subjecting the blend of sucrose, water, and shortening to high shear or including in the frosting an emulsifier and/or pregelatinized starch or cold water soluble pectin to act as bodying agents.
Daggy, U.S. Pat. No. 3,649,302, issued Mar. 14, 1972, discloses yet another storage-stable ready-to-spread frosting. The Daggy frosting has two components: about 55 to 85 weight percent of a "comminuted sugar phase" and 15 to 45 weight percent of a "glyceridic-oil-phase-in-aqueous-phase emulsion". The former comprises 45 to 70 weight percent sucrose and 30 to 55 weight percent dextrose. The latter comprises a glyceridic oil such as margarine oil, shortening, or butter oil; water; and emulsifier; and a cold-water-swelling starch or cellulose.
Blake, U.S. Pat. No. 4,232,049, issued Nov. 4, 1980, discloses a frosting which is substantially fat-free but which allegedly has the rich mouthfeel of creme frostings and the lightness of fluffy frostings. The frosting comprises: (a) about 90 to 98 percent of a "comestible base"; (b) about 0.4 to 3 percent of a whipping agent, such as the protein hydrolyzates sold by the A. E. Staley Manufacturing Company; and (c) about 0.1 to 0.5 percent of a polysaccharide gum such as guar gum, locust bean gum, and xanthan gum. The "comestible base" is prepared by cooking a blend of: (1) about 25 to 65 percent citrus juice vesicles; (2) about 7 to 45 percent nutritive carbohydrate sweetener; (3) about 1 to 5 percent ungelatinized starch; (4) about 8 to 60 weight percent water; and (5) edible acid.